For some buckles used to connect and disconnect both ends of a string member or the ends of the two string members, there has been suggested an arrangement capable of preventing rattling of a socket and a plug inserted in the socket (see, for instance, Patent Literature 1).
In this case, a buckle includes a plug and a socket. The plug includes a plug body, a pair of legs that project from both lateral ends of the plug body in parallel with each other, and a guide bar that projects in parallel with the pair of legs from a position between the pair of legs. The outer lateral sides of the legs are provided with engagement grooves that are opened in an opposite-insertion direction. A spring is integrally provided to the distal end of the guide bar in parallel with the legs. The socket includes a cylindrical socket body, openings provided to both lateral walls of the socket body such that the legs of the plug are exposed outside, and engaged portions that are provided to the lateral walls to which the openings are provided and are respectively engaged with the engaging grooves of the plug.
In the arrangement, in order to engage the plug with the socket, the legs of the plug are inserted into the socket. While being inserted into the socket, the distal ends of the legs are each elastically deformed inward by both lateral walls of the socket. Simultaneously, the spring is gradually compressed. When the engaging grooves of the legs pass the engaged portions of the socket, the legs, which have been elastically deformed inward, are elastically recovered outward. At this time, when the insertion of the plug is stopped, the plug is biased in the opposite-insertion direction by the resilience of the compressed spring, so that the engaging grooves of the legs are engaged with the engaged portions, respectively.
In order to disengage the plug from the socket, the plug is pushed into the socket and, then, the legs of the plug exposed out of the openings of the socket are pushed inward, thereby disengaging the engaging grooves from the engaged portions. In this state, the plug is pushed out of the socket with the assistance of the resilience of the spring. Thus, the plug can be disengaged from the socket.    Patent Literature 1: DE19837071A1